The present invention relates to 2-alkoxy-4-hydrazinopyrimidine compounds and to their use in the preparation of 5-alkoxy-1,2,4-triazolo[4,3-c]pyrimidine-3(2H)-thione compounds.
5-Alkoxy[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide compounds that are potent herbicides are described in U.S. Pat. No. 5,163,995 and are disclosed therein to be prepared in a multistep process from appropriately substituted 2-alkylthio-4-hydrazinopyrimidine compounds. The preparation requires a cyclization with carbon disulfide, a rearrangement, and a substitution reaction wherein the alkylthio moiety is replaced with an alkoxy moiety in the presence of an ethylenically unsubstituted compound capable of reacting with and removing the displaced alkanethiol. This process is lengthy, produces the desired products in only moderate yield, and results in a by-product alkylthioethyl moiety-containing compound which must be disposed of as waste. Improved methods for preparing herbicidal 5-alkoxy[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide compounds, including improved methods for preparing intermediates that are useful in their preparation, would be of considerable value as would the starting materials and intermediates that would be required to implement the improved methods.
A few 2-alkoxy-4-hydrazinopyrimidine compounds are known in the art and are known to be useful as chemical intermediates (e.g., Chem. Pharm. Bull., 17, 1467-78 (1969) and J. Chem. Soc. 1970, 2661-66). The halogenated 2-alkoxy-4-hydrazinopyrimidine compounds that would be required to produce herbicidal N-(substituted phenyl)-5-alkoxy-(7- or 8-halo)[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide compounds, however, have not been described.
5-Alkoxy-1,2,4-triazolo-[4,3-c]pyrimidine-3(2H)-thione compounds have not been described in the art.